NAME¶
Padre::Document::Perl::Beginner - naive implementation of some beginner specific
error checking
SYNOPSIS¶
use Padre::Document::Perl::Beginner;
my $beginner = Padre::Document::Perl::Beginner->new;
if (not $beginner->check($data)) {
warn $beginner->error;
}
DESCRIPTION¶
This is a naive implementation. It needs to be replaced by one using PPI.
In Perl 5 there are lots of pitfalls the unaware, especially the beginner can
easily fall in. While some might expect the Perl compiler itself would catch
those it does not (yet ?) do it. So we took the initiative and added a
beginners mode to Padre in which these extra issues are checked. Some are real
problems that would trigger an error anyway we just make them a special case
with a more specific error message. (e.g. "use warning;" without the
trailing s) Others are valid code that can be useful in the hands of a master
but that are poisonous when written by mistake by someone who does not
understand them. (e.g. "if ($x = /value/) { }" ).
This module provides a method called "check" that can check a Perl
script (provided as parameter as a single string) and recognize problematic
code.
Examples¶
See <
http://padre.perlide.org/ticket/52> and
<
http://www.perlmonks.org/?node_id=728569>
Cases¶
- •
-
split /,/, @data;
Here @data is in scalar context returning the number of elements. Spotted in
this form:
split /,/, @ARGV;
- •
-
use warning;
s is missing at the end.
- •
-
map { $_; } (@items),$extra_item;
is the same as
map { $_; } (@items,$extra_item);
but you usually want
(map { $_; } (@items)),$extra_item;
which means: map all @items and them add $extra_item without mapping
it.
- •
- Warn about Perl-standard package names being reused
package DB;
- •
-
$x = chomp $y;
print chomp $y;
- •
-
map { s/foo/bar/; } (@items);
This returns an array containing true or false values (s/// - return value).
Use
map { s/foo/bar/; $_; } (@items);
to actually change the array via s///.
- •
-
<@X>
- •
-
if ($x = /bla/) {
}
- •
- Pipe | in open() not at the end or the beginning.
- •
-
open($ph, "| something |");
- •
- Regular expression starting with a quantifier such as
/+.../
- •
-
} else if {
- •
-
} elseif {
- •
-
close;
HOW TO ADD ANOTHER ONE¶
Please feel free to add as many checks as you like. This is done in three steps:
Add the test¶
Add one (or more) tests for this case to
t/75-perl-beginner.t
The test should be successful when your supplied sample fails the check and
returns the correct error message. As texts of error messages may change, try
to match a good part which allows identification of the message but don't
match the very exact text.
Tests could use either one-liners written as strings within the test file or
external support files. There are samples for both ways in the test script.
Add the check¶
Add the check to the check-sub of this file (
Document/Perl/Beginner.pm).
There are plenty samples here. Remember to add a sample (and maybe short
description) what would fail the test.
Run the test script to match your test case(s) to the new check.
Add the configuration option¶
Go to
Config.pm, look for the beginner error checks configuration and add
a new setting for your new check there. It defaults to 1 (run the check), but
a user could turn it off by setting this to 0 within the Padre configuration
file.
COPYRIGHT & LICENSE¶
Copyright 2008-2013 The Padre development team as listed in Padre.pm.
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this
module.